1984 was not a great year for GM drivetrains.
The 700-R4 prior to 1987 had a weak pump, but if your motor is stock, and the fluid is good, you could use it with a vacuum lock-up kit. Need to shorten the G-body driveshaft 3". Obtain a Jegs or Summit crossmember for the 700-R4.
If it has a 10-bolt axle, the guts will swap to your 7.5 with no changes. Disc bakes can be made to work if it had them.
Front sway bar will swap. Rear lower control arms will swap, I think.
Power steering box is an upgrade if it has the square top with four bolts and yours has the round top. Can't remember if the pitman arm is the same. There may be a power steering cooler line you can use.
Front seats will swap onto your slider brackets. Console may exchange with modifications. Shifter will work using the stock cable. You could swap the handbrake in with a little engineering of the cables.
Front springs may swap, no idea whether they would be an improvement over your stock ones.
Manifolds are the same, but the Y-pipe is all wrong. If the muffler is recent, it and the tail pipes could be reworked with a bit of welding.
